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Calculating wet topsoil pile weight

Calculating wet topsoil pile weight. Calculate the moisture content (w): w = [(g water) / (g dry soil)] x 100 = % Calculate dry topsoil weight using Db (g dry soil/bulk volume): vol (m 3 ) x Db (Mg/m 3 ) = dry weight of pile (Mg) Rearrange the first eqn to solve for wet soil wt.

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Calculating wet topsoil pile weight

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  1. Calculating wet topsoil pile weight Calculate the moisture content (w): w = [(g water) / (g dry soil)] x 100 = % Calculate dry topsoil weight using Db (g dry soil/bulk volume): vol (m3) x Db (Mg/m3) = dry weight of pile (Mg) Rearrange the first eqn to solve for wet soil wt. g wet soil = Dry soil wt x (1 + w/100)

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  4. Ch. 8 continued Estimating and Calculating CEC

  5. What is the source of charge on colloids? • Isomorphic substitution (2:1 clays) Iso (same) morph (shape) • an ion of similar size, but not necessarily the same charge, can replace another during formation of the crystal and result in a net charge without disrupting the crystal. • Deprotonation (remove H+ to get negative) or protonation (add H+ to get positive) Humus, 1:1 clays, Fe & Al oxides

  6. Cation exchange on negatively charged sites (Mg substituting for Al in Octahedral sheet) Isomorphic substitution Mg deprotonation

  7. Note all the potential sites for ‘deprotonation’, or removing a H+ which will give you a negative site to attract cations.

  8. Broken edges of minerals can “de-protonate” or “protonate” and become chargedAs pH increases, CEC increases

  9. Characteristics of Ion Exchange • Electrostatic (charge) interactions • Rapid • Exchange requires nearby proximity of one ion for another • Reversible • Stoichiometric - ions on surface are exchanged with equivalent (number of charges) amounts of other ions (not molar amounts). 2 Na+ exchange for 1 Ca+2 3 Na+ exchange for 1 Al+3 • Selective - some ions are preferred (more tightly held) over others.

  10. The predominant cations on the exchange complex and the order of strength of adsorption include: Al+3 > Ca+2 > Mg+2 > K+ = NH4+ > Na+ • The strength of adsorption is dependent on the charge of the cation and the size of the hydrated cation Usually, higher charge and smaller hydrated radius results in stronger adsorption • Less tightly held cations oscillate farther from colloid surface Therefore, more likely to be displaced into solution or leached • Multivalent cations help flocculate soils; sodium disperses soils (large radius, low valence)

  11. http://www.physchem.co.za/Atomic/Graphics/GRD50005.gif

  12. http://boomeria.org/chemlectures/textass2/table10-9.jpg

  13. http://www.gly.fsu.edu/~salters/GLY1000/6_Minerals/6_Minerals_index.htmlhttp://www.gly.fsu.edu/~salters/GLY1000/6_Minerals/6_Minerals_index.html

  14. CEC range for common soils and materials at pH 7 Note: Very high CEC of humus (soil organic matter); High CEC for 2:1 clays; Low CEC for sandy soils, 1:1 clays, Fe & Al oxides

  15. Estimating CEC based on soil components E.g., estimate the CEC of a soil with pH = 7.0; 20% clay; 4% organic matter; assume: (CEC of clay = 80 cmolc/kg); (CEC of OM = 200 cmolc/kg); CEC associated with clay = 0.2 * 80 cmolc= 16 cmolc CEC associated with OM = 0.04*200 cmolc = 8 cmolc Total CEC = 16 + 8 = 24 cmolc per kg soil

  16. Common estimate values cmolc for Colloideach 1% colloid 2:1 Silicate Clay ------------------- 0.5 1:1 Silicate Clay ------------------- 0.1 Fe or Al oxide Clay --------------- 0.1 Organic Matter (humus)----------- 2.0

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